In recent years, there is a need for a more efficient driving motor for a blower, smaller than a conventional motor, for a vehicle air conditioner or a ventilation device for a hybrid vehicle. Thus, there is required development of a driving motor having excellent water-proof and heat releasing characteristics, having a smaller size along the axial direction of a rotating shaft of a blower, and reducing the manufacturing cost.
In this case, for example, a vehicle-mounted blower equipped with a brushless motor as mentioned in Patent Document 1 is already known. The vehicle-mounted blower disclosed in Patent Document 1 is provided with a brushless motor that rotates a blower fan, a cooling fin molded in a single body in a metallic housing of the brushless motor, an auxiliary blade arranged in the blower fan to produce an air flow around the cooling fin, and a driving element closely attached to the housing. The objective thereof is to increase the cooling capacity of the motor driving element and reduce the size in a height direction of the blower as well as to take measures to curtail the manufacturing cost by reducing the number of parts.
Moreover, it is known that when an external air introducing mode is selected in the blower unit of the vehicle air conditioner and the external air is introduced from outside the vehicle interior, in case of rain, a misty rain water together with the external air enters the blower so that water drops adhere to electric devices such as an armature, contained in the driving motor and give rise to a problem of the insulation of the electric devices such as an armature, or a problem of rust such as in the component parts.
In response thereto, as mentioned in Patent Document 2, there is known a motor configured such that an interior space is formed by a metallic casing extended in an umbrella shape that opens from a rotating shaft below both blade wheel boss part and cone part that extends from the boss part, and a non metallic (for example, resin made) bottom plate that can cover a lower opening of this casing, the armature is housed in the interior space, and the casing and the bottom plate are fixed tightly and closely by screwing outwardly extending two flanges formed at the circumferential edge.
Moreover, there is already known a brushless motor as disclosed in Patent Document 3, for example. Although the brushless motor is directed at the use for a compressor unit of a home use air-conditioner rather than the blower unit of the vehicle air conditioner, it has a structure to prevent water from entering the motor interior-space when this compressor unit of the air conditioner is sprayed with water. In short, the brushless motor has a water-proof structure including a cylindrical casing. The cylindrical casing has a stator to be protected from water and is divided into left-right two cup-shaped casings at a vertical plane in the general center of the size of a rotating shaft direction. On a surface formed by connecting the left-right cup-shaped casings, a protrusion is arranged on one surface of the cup-shaped casing and a groove is arranged on the other surface of the cup-shaped casing, the protrusion is inserted into the groove, and an O-shaped ring is provided between the groove and the protrusion, whereby the left-right cup-shaped casings are air-tightly joined.
Moreover, Patent Document 4 discloses a driving motor for a blower unit of a vehicle air conditioner having a structure wherein a rotor assembly is rotated by appropriately switching the magnetic power between a stator assembly and a rotor assembly, which are component parts of a magnetic circuit, and a rotating shaft is rotated along therewith. In this Document, it is known that magnetic vibrations are generated in a rotating direction (a radial direction of the rotating shaft) of the driving motor at the time of switching the magnetic power. Further, a driving motor for a blower unit of a vehicle air conditioner is disclosed in FIG. 5 of Patent Document 4. The driving motor is structured such that a rotor member such as a multi-blade fan is attached to one side end along an shaft direction of a rotating shaft and the rotor member is rotated to take in air and blow air in a predetermine direction. In this technology, it is known that there occurs a movement in which both ends of the rotating shaft rotate while drawing a circle as if to squeeze a pestle (hereinafter referred to as “precession”) from various factors such as an air flow taken in or minute core misalignment of the rotating shaft.
If the two vibration components, magnetic vibration and vibration due to precession, are kept as it is, noise will be generated from the driving motor. In order to control these vibrations, a structure of the brushless motor is described in the claims of Patent Document 4. The rotor is rotatably supported in the stator and the lower end of the center piece of the stator is fixed in the motor holder through a vibration-proof material. Then, the structure of a vibration-proof material of the brushless motor disclosed in Patent Document 4 is summarized by describing the detailed description of Patent Document 4. The vibration-proof material is made of rubber having hardness from 20 to 40 in a generally cylindrical shape with a cylindrical through-hole in the central part. The inner diameter has the smallest size in the central region in the axial direction of the through-hole, and the inner diameter of the through-hole gradually expands towards the both openings. An annular groove is formed in the axial direction central region of the rubber cylinder outer surface.